Breast cancer is one of the most common causes of cancer in women. The likelihood of developing invasive breast cancer during a woman's lifetime is approximately 1 in 7. In 2003, the global market for breast cancer was estimated at US $5 billion and is expected to rise to US $11.6 billion by 2008. For example Herceptin, a targeted therapy for women with early-stage HER2-positive breast cancer has enjoyed double-digit sales growth every year since its launch in 1998. Recently, Herceptin had a 58% spike in sales to $764 million after the release of the data for it use in early-stage breast cancer.
There is no standard treatment for breast cancer, where the current methods range from surgery and radiation, to chemotherapy, hormone therapy, and biological therapy (including, monoclonal antibody therapy) and combinations thereof. The type of treatment chosen is generally governed by the stage and type of cancer at the time of diagnosis.
Considerable commercial and academic resources are directed to identification of candidate therapeutic agents for the treatment of breast cancer. For example, Herceptin is a humanized antibody approved for the treatment of HER2-positive metastatic breast cancer. Herceptin is designed to target and block the function of HER2 protein, a growth factor protein that is overexpressed in approx 25% of breast cancer patients. A further example, Tykerb, is a dual kinase inhibitor which inhibits both ErbB-2 and EGFR kinases and may be more effective than Herceptin.
Like numerous forms of cancer, breast tumour growth is a multifactorial disease with no standardised medication available for patients. In spite of major advances in early detection and adjuvant therapy, advanced breast cancer remains a major clinical and social problem.